1. Field of the Invention
The present invention relates to technology for displaying moving images by consecutively displaying a plurality of frame images, and more specifically relates to technology for synthesizing a plurality of frame images and generating an intermediate frame image.
2. Description of the Related Art
In the past, when displaying images on a moving image display device such as a CRT, television or the like with a refresh rate of less than 60 Hz, there were cases when flicker (blinking) occurred on the overall screen. However, even when a sufficient refresh rate is secured, in cases when displaying moving images such as when a moving object moves on the screen, there were cases when flicker occurred only in the moving object part on the screen rather than on the overall screen. Hereafter, this kind of flicker is called “moving image flicker.” This kind of phenomenon occurs frequently, for example, when displaying moving images that move at a fixed speed such as a person, car, airplane or the like within the screen, or moving images when panning the video camera at a fixed speed.
This kind of phenomenon is not limited to CRTs and televisions, but is also seen in cases when displaying moving images on moving image display devices such as liquid crystal displays, plasma displays, projectors or the like, on the display unit of a PDA, mobile phone or the like, or on the screen in a movie theater or the like, and this was a problem common to moving image display. There were cases when once the viewers became bothered by the existence of the moving image flicker described above, they felt stress while viewing.
Regarding this kind of problem, for example in JP-A-04-302289, disclosed is technology for displaying moving images smoothly by dynamically generating new intermediate frame images from two frame images to suppress the unnaturalness of the movement when displaying moving images in a liquid crystal moving image display device or the like having an approximately 100% light emitting time ratio. In specific terms, as shown in FIG. 2 of patent reference 1, if it is a video image for which a round mark moves from left to right on the screen, by newly drawing round marks that are at two positions intermediate to the round mark within the before and after frames, an intermediate frame image is generated.
Also, disclosed in JP-A-2001-296841 is technology that detects whether an input video image is a moving image or a still image, and when a moving image is displayed, switches to the optimal display method for moving image display by taking action to double the field frequency or the like.
However, with the prior art described above, because it is necessary to generate a completely new intermediate frame from two frame images, the calculation processing for this becomes huge, so it was difficult to improve the moving image display speed. Also, to generate a completely new intermediate frame, it is necessary to secure a large frame memory capacity, and this became a factor in increasing costs. Also, when switching the display method with moving images and still images, there was concern that smooth video image display would not be possible due to the occurrence of a virtual image during switching of the display method or the like.